Research On Effect Of Low Temperature At Booting And Flowering Stage On The Rice Yield Based On ORYZA2000 Model In Shenyang Region

Frequency of extremely weather due to the global warming was higher in recent years,which made a huge influence on the agricultural production in China.Rice is the staple food crop in China,whose growth and development is really sensitive to temperature.The northeast region of China is one of the most important rice cultivation areas,however,the chilling damage,considered as a common agricultural meteorological disaster,would reduce rice yield,and it impacted the agricultural sustainable development as well.This research uses methods of field experiment and model simulation,predicts rice yield in the future climatic conditions with the advanced crop model which is based on actual experiment measured data,and to find out adaptive strategies.The results play an important role in food security and national stability.This research takes 9023,9035,9036 as the representative varieties of mid-early,mid and mid-late rice varieties in Shenyang region,respectively.Manual artificial weather box was applied to simulate chilling environment,and the temperature setting is 17 Celsius degrees at the booting stage and 19 Celsius degrees at the flowering stage,four different low temperature duration time and recovering time are set as well.We use LI-6400 Photosynthetic meter to measure spectral response curves of rice 2nd leaf from top under all the treatments,and FMS-2 fluorescence to measure chlorophyll a fluorescence parameters in order to analyze the effect of chilling damage on photosynthesis and fluorescence parameters of rice.Measure the number of spikelets and spikelets fertility rate,establish the numerical relation equations between duration days of low temperature and two factors mentioned above to improve the ORYZA2000 model.Finally,analyze the change of 9023,9035,9036,rice yield in the future with the advanced model combined with CMIP5 climatic data as well as explore the strategies of changing sowing date and cultivate new rice varieties.The results are as follows:1.Chilling damage at the flowering stage rendered the decreases of net photosynthesis of 9023(mid-early),9035(mid)and 9036(mid-late)as the recovering time increases.Longer the low temperature time and recovering time were,bigger descend range of net photosynthesis was.And 9023(mid-early)was more sensitive to recovering time,while 9035(mid)was more sensitive to duration time of low temperature,and 9036(mid-late)was equally sensitive to both two factors.After suffering chilling damage,decreases of three varieties' photosynthetic rates are mainly due to non-stomatal factors.2.Potential photosynthetic capacity of 9023(mid-early)under different low temperature treatments did not change significantly compared with CK,but the actual photosynthetic ability suggested a tendency of decline.After suffering chilling damage at booting stage,fluorescence parameters of 9035(mid)and 9036(mid-late)were lower than that at flowering stage in a whole,indicating that chilling damage at flowering stage would influence photosynthesis more.Furthermore,fluorescence parameters of 9035(mid)and 9036(mid-late)were lower than that of 9023(mid-early),showing the higher cold endurance of 9023,which accorded with the variety characteristic.3.According to the future climatic data,there will still be a large number of chilling days in the mid and end of the 21 st century,especially for late ripening varieties,suggesting that the chilling damage of rice will still proceed under the global warming.4.The numerical relation equations between low temperature and the number of spikelets and spikelet fertility rates were set by experiment data,and ORYZA2000 model was improved by the equations and was calibrated and validated by field experiment data in 2017 and 2018.Results showed the good ability to predict rice yield of seven varieties of the model.5.Simulation results from advanced ORYZA2000 model showed that yield of Shenyang native variety Shennong 263 would reduce under the BCC-CSM1.1 and CSIRO-Mk3.6.0 models,while increase under Had GEM2-ES model.In the future climatic environment,yield of mid and mid-late maturity varieties shows a increasing trend,but mid-early maturity varieties yield will reduce.For three exotic varieties,Yanfeng 47 has a better ability to increase yield.6.There are two adaptive strategies including changing sowing date and cultivating new varieties can be applied to adapt to the future climate.Under CSIRO-Mk3.6.0 model,yield of 9035,9036 and Yanfeng 47 can be increased by setting a specific earlier sowing date,yield of 9035 and 9036 can also be improved by setting a later sowing date.Cultivate new varieties whose growth and development rate is low especially at panicle initiation stage is also a new method to increase the rice yield in the future.